Advancement of prop blade in flight, new information

Corky

Computer dropped my add on to your posting so will try again.

Besides the round engines, the V's also had gearing. The Merlin in the
P-51 had a two to one (ie, engine ran 3000 rpm on take off and prop
turned 1500 rpm).

Big John

On Tue, 17 Aug 2004 08:03:06 -0400, Corky Scott
wrote:



You don't see that so much anymore in

"AJW" wrote in message news:20040816181349.12901.00001819@mb-
I don't know of a SEL airplane in general use that uses reduction gearing
between the shaft and the prop, Dan.

My old Navion, Helio Couriers, Republic Seabees, Cessna 175's...
Lots of Rotax powered light planes...


Not overly common, but they are out there.

"DanH" wrote in message
...
AJW wrote:

[snip]
For what it's worth, at 150 kts and 2500 RPM means the airplane advances
about
6 feet per prop rev. A two bladed prop means each balde is in air 3 feet
ahead
of the prior blade.

That's the same number I came up with, but that assumes there's a
one-to-one ratio between engine RPM and prop RPM. Is that true of all
single engine piston aircraft? I'm obviously not an AC mechanic, but I
thought I could see a reduction gear in the cowl.

DanH

In addition, the term "slippage" comes into play. That's the difference
between the theoretical distance the prop should advance with each
revolution and the actual.

And besides a reduction gear creating a difference between engine and prop
RPM, a constant speed prop gives control of the prop speed to the pilot or
the prop governor mechanism.

--
Scott

"tscottme" wrote in message
...
In addition, the term "slippage" comes into play. That's the difference
between the theoretical distance the prop should advance with each
revolution and the actual.

The slippage is only related to a theoretical number based on the prop
pitch. For the purpose of this discussion, the only interesting thing is
the prop RPM versus forward speed.

DanH wrote:

I'm obviously not an AC mechanic, but I
thought I could see a reduction gear in the cowl.

That was probably the flywheel -- they have toothed edges to mesh with the starter.
If gears are used for a reduction system, they are likely to be enclosed in a
housing; you wouldn't be able to see them.

George Patterson
If you want to know God's opinion of money, just look at the people
he gives it to.